Comment 3 for bug 834174

The issue seems to be in /usr/share/initramfs-tools/hooks/dropbear, which contains this line:

cp /lib/libnss_* "${DESTDIR}/lib/"

The path to libnss_files seems to have changed, I think due to multiarch. If you change the line to (assuming you are using a 64-bit ubuntu):

cp /lib/x86_64-linux-gnu/libnss_* "${DESTDIR}/lib/"

Then you should be able to log into dropbear in the initramfs again. This doesn't make remote unlocking work perfectly however, as apparently there's some interaction between plymouth and the script that takes the passphrase on the console that breaks things. There's a workaround for that particular problem at:

http://blog.nguyenvq.com/2011/09/12/remote-unlocking-luks-encrypted-lvm-using-dropbear-ssh-in-ubuntu/